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    Subject[PATCH 005 of 10] md: raid1: Fix restoration of bio between failed read and write.

    When performing a "recovery" or "check" pass on a RAID1 array,
    we read from each device and possible, if there is a difference or a
    read error, write back to some devices.

    We use the same 'bio' for both read and write, resetting
    various fields between the two operations.

    We forgot to reset bv_offset and bv_len however.
    These are often left unchanged, but in the case where there is an
    IO error one or two sectors into a page, they are changed.

    This results in correctable errors not being corrected properly.
    It does not result in any data corruption.

    Cc: "Fairbanks, David" <David.Fairbanks@stratus.com>
    Signed-off-by: Neil Brown <neilb@suse.de>

    ### Diffstat output
    ./drivers/md/raid1.c | 15 +++++++++++++--
    1 file changed, 13 insertions(+), 2 deletions(-)

    diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
    --- .prev/drivers/md/raid1.c 2008-05-19 11:03:05.000000000 +1000
    +++ ./drivers/md/raid1.c 2008-05-19 11:02:55.000000000 +1000
    @@ -1284,6 +1284,7 @@ static void sync_request_write(mddev_t *
    rdev_dec_pending(conf->mirrors[i].rdev, mddev);
    } else {
    /* fixup the bio for reuse */
    + int size;
    sbio->bi_vcnt = vcnt;
    sbio->bi_size = r1_bio->sectors << 9;
    sbio->bi_idx = 0;
    @@ -1297,10 +1298,20 @@ static void sync_request_write(mddev_t *
    sbio->bi_sector = r1_bio->sector +
    conf->mirrors[i].rdev->data_offset;
    sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
    - for (j = 0; j < vcnt ; j++)
    - memcpy(page_address(sbio->bi_io_vec[j].bv_page),
    + size = sbio->bi_size;
    + for (j = 0; j < vcnt ; j++) {
    + struct bio_vec *bi;
    + bi = &sbio->bi_io_vec[j];
    + bi->bv_offset = 0;
    + if (size > PAGE_SIZE)
    + bi->bv_len = PAGE_SIZE;
    + else
    + bi->bv_len = size;
    + size -= PAGE_SIZE;
    + memcpy(page_address(bi->bv_page),
    page_address(pbio->bi_io_vec[j].bv_page),
    PAGE_SIZE);
    + }

    }
    }

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